1. Field of the Invention
The present invention pertains to amphiphilic organopolysiloxanes having a high refractive index, which readily emulsify or self-emulsify in aqueous preparations to form micro- or macro-emulsions, are free of cyclic organopolysiloxanes, and bear arylalkyl, long chain alkyl, and hydrophilic groups along the polymer chain.
2. Background Art
Polydimethylsilicones, optionally functionalized, have long been used in a variety of applications including cosmetics and personal care products such as shampoos and conditioners. Unfortunately, such silicones suffer from a relatively low refractive index. In the personal care sector especially, there is an increasing emphasis on high gloss in hair care products. Such products also have uses in cleaning products such as waxes and polishes.
Personal care consumer products such as shampoos, conditioners, skin care formulations and color cosmetics articles often derive high or higher aesthetic and commercial value from the shine and/or gloss benefits that they impart. Ingredients with a refractive index (RI) of greater than about 1.44 can lead to distinct/discernible shine/gloss perception on keratinous and skin surfaces. Aryl substituents in both small molecules and polymers are a preferred way to raise the RI of ingredients used for shine in personal care formulations. High-RI arylated silicones (both homo- and copolymers with dimethylsiloxane) containing either Ar—Si moieties or aralkyl substitution on silicon are widely known in the literature and the personal care industry, although molecules with the Ar—Si unit are most commonly used in personal care, particularly, ingredients such as phenyl trimethicone (INCI nomenclature) and sold in the market, e.g., as Dow Corning® 556 Fluid.
Arylalkylsilicones of high refractive index are known from U.S. Pat. No. 5,384,383, and are prepared by hydrolytic condensation of 2-phenylpropylmethyldichlorosilanes. However, the preparation leads to high quantities of cyclic products which may be environmentally or toxicologically suspect. A comparative preparation by hydrosilylation of α-methylstyrene is taught by U.S. Pat. No. 5,384,383 to be deficient in that the product has a strong odor of α-methylstyrene.
It is of note that the above arylated and arylalkylated silicones are primarily used in the oil phase of the formulation due to their compatibility with common formulation ingredients such as natural oils, synthetic esters and hydrocarbons. The trend toward water-based formulations and especially clear, water-based formulations in personal care is steadily increasing, following the desire of the consumer to use more “natural” and “organic” products. There is, therefore, a distinct need to provide the benefit of shine/gloss via aryl-containing siloxanes that are compatible with or readily compatibilized in polar formulation media, particularly water, without significantly compromising oil compatibility. Such amphiphilic and versatile, arylalkyl-containing silicones of general utility have not been available commercially.
U.S. Pat. No. 6,133,370 discloses the preparation of silicones which contain both arylalkyl moieties and polyether moieties. However, the preparation methods enabled by the '370 patent all involve either a cohydrolytic condensation of appropriately substituted chlorosilanes or the use of an equilibration reaction, and thus the products all contain a significant proportion of suspect cyclic compounds. Only the introduction of the polyether moieties is achieved by hydrosilylation. In the process of the '370 patent, it is exceptionally difficult to remove arylalkylated cyclic species from the reaction product. There is no indication that the products of the '370 patent are capable of either self-emulsification in water or micro-emulsion formation, nor would they be expected to be.